The long range objectives of this research project with intact mice and rats are to (1) elucidate the mechanisms of in vivo protective systems which are dependent on vitamin E, (2) relate these protective systems to mechanisms of chemically induced toxicity including oxidative stress and damage, and (3) investigate the interactions of these protective systems using intact animals for interorgan considerations. In Specific Aim l, studies are proposed to elucidate the mechanism by which vitamin E is secreted into the bile under both physiologic and pathologic conditions, including chemically altered bile secretion. We will determine the extent to which vitamin E secreted into the bile is reabsorbed under both normal and pathologic conditions to test the hypothesis that canalicular mdr2 P-glycoprotein is important in the biliary secretion of vitamin E. We will use the recently developed mdr2 knockout mice, which lack phospholipids in their bile, to investigate the relationship between vitamin E status and phospholipid homeostasis. In addition, as part of specific aim l we will study the relationship between vitamin E status, and the biliary secretion of vitamin E, and GSH homeostasis using the gamma-glutamyl transpeptidase (GGT) knockout mice recently developed in the laboratory of Dr. Michael Lieberman, Baylor University. A collaborative study with Dr. Daniel Liebler, University of Arizona, is proposed in Specific Aim 2 to investigate the in vivo consumption and oxidation products of vitamin E. Our hypothesis is that the oxidation product profile of vitamin E will vary with the mechanism of oxidative challenge and the GSH status of the animal; certain oxidation products, which can be detected in the blood, may serve as biomarkers of the extent of hepatic oxidative stress. These experiments are expected to provide a better understanding of the possible in vivo "sparing" effect of GSH and vitamin E under pathologic conditions. In Specific Aim 3 we will use a strain of Wistar rats which are unable to produce vitamin C to investigate the turnover of vitamin E and oxidation products formed under both normal metabolic and oxidative stress conditions; we will use diets which provide 3 levels of both vitamin E and vitamin C. Our hypothesis is that vitamin C status will have an effect on the turnover of vitamin E, as well as the quantity and species of vitamin E oxidation products, when comparing animals with low v.s. high tissue vitamin E levels under pathologic conditions.